1. Field of the Invention
The present invention relates to the cooling of an enclosure having a heat source disposed therein and, in particular, to a passive system for accomplishing the internal cooling of a surgical lighthead assembly.
2. Description of the Prior Art
In diverse environments there are found devices, such as lights, in which a heat generating means is contained within a sealed enclosure. It will be readily appreciated that due to the heat produced within such enclosure by the heat generating means, the temperature in the enclosure can quickly rise to levels sufficient to damage the componentry internal to the enclosure.
An example of a device such as described above is a surgical lamp which may comprise a plurality of lamps sealed within an enclosure. An enclosed lighting system employing a plurality of lamps therein generates a large amount of heat within the light fixture. This is especially true of surgical lighting systems where, due to the requirements of the surgical process, most of the heat-producing infrared light must be removed from the generated illumination pattern and is instead radiated into the fixture.
Due to the sterility requirements of various "clean areas", surgical lights should be sealed to the environment. Such sealing is required to prevent contaminants from being drawn over the surgical site by thermal currents particularly when the surgical light is used in close proximity thereto. In addition, these contaminants will deposit on internal optical componentry and degrade reflective and transmissive properties. Overall optical efficiency will then diminish over time.
One prior art method of accomplishing the cooling of a surgical light is shown is U.S. Pat. No. 4,037,096. That patent teaches of the provision of slots in the outer housing thereof sufficient to allow air to circulate into and out of the enclosure to cool the heat generating source and remove the heat to the atmosphere. Unfortunately, as noted above, the provision of slots within the surgical light's outer housing allows dust, bacteria and other contaminants to enter the surgical light which will then be transmitted therefrom to the surgical site when the surgical light is introduced thereinto or foul the optical characteristics of the system. As such, the prior practice of providing cooling slots to allow air flow through the light is clearly inadequate to serve the paramount interests of sterility found in a surgical environment and of lighting efficiency needed to ensure adequate illumination.
Another prior art means of cooling a heat source disposed within an enclosure, such as a surgical light, includes a fan means operative to circulate cooling air past the heat generating source. It is manifest that the provision of such an air circulating fan also requires the installation of vents to allow air flow into and out of the enclosure. From above, such air vents provide access for contaminants to enter the light and to travel to the surgical site. Moreover, the action of the fan will draw higher amounts of contaminants due to its increased flow rates over the surgical site thereby further exacerbating the problems of contamination and interference with the lighting pattern. In addition, the use of a fan in a surgical light adds excessive noise to the surgical theatre and causes the vibration of the light which interferes with overall lighting efficiency.
The subject invention is directed toward an improved means for withdrawing heat from an enclosure having an internal heat generating source which overcomes, among others, the, above-discussed problems and provides a means for passively cooling an enclosure having an enclosed heat source without requiring passages to the atmosphere or a vented fan means.